High-Frequency Phase Dithering for Analog Optical Fronthaul Noise
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Solution Overview
Problem
Analog optical transmission-based mobile fronthaul networks face interference noise issues due to multipath interference from defective optical connectors, which affect signal quality and fail to meet 5G communication standards, especially with high error vector magnitude (EVM) requirements.
Innovation Solution
A high-frequency phase dithering technique is employed to modulate the phase of an optical signal, using an orthogonal frequency division multiplexing (OFDM) signal with a specific modulation index and bandwidth, to suppress interference noise by converting it out of the signal band, and an optical phase modulator is used to dither the intensity-modulated optical signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-frequency phase dithering is applied to suppress interference noise, then signal quality is improved, but optical signal spectrum broadening occurs and chromatic dispersion increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the frequency and amplitude of the phase dithering signal. Specifically, the dithering frequency is set to be higher than the signal bandwidth to move interference noise out of the signal band, while the modulation depth is optimized to achieve noise suppression without excessive spectrum broadening. This resolves the contradiction by finding optimal parameter values that balance signal quality improvement with acceptable spectrum expansion.
Solution Approach 2:
The patent implements dynamic adjustment of phase dithering parameters based on transmission conditions. The system dynamically optimizes the dithering frequency and modulation depth according to the actual signal characteristics and channel conditions, allowing adaptive suppression of interference noise while minimizing spectrum broadening effects. This dynamic approach enables the system to maintain signal quality while controlling the degree of spectrum expansion.
2Object-affected harmful factors
If phase dithering frequency is increased to move interference noise out of signal band, then interference noise suppression is improved, but line width of optical signal significantly increases
Solution Approach 1:
The patent resolves this contradiction by establishing an optimal relationship between dithering frequency and signal bandwidth. The dithering frequency is set to a specific value higher than the signal bandwidth to effectively move interference noise out of the signal band, while the modulation depth is carefully controlled to limit line width expansion. This parameter optimization ensures that interference noise is suppressed without causing excessive broadening of the optical signal line width.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The technique effectively reduces interference noise, ensuring the analog optical transmission scheme meets signal quality requirements even with multiple defective optical connectors, by optimizing the frequency position, modulation depth, and bandwidth of the high-frequency phase dithering signal, thereby guaranteeing performance in the mobile fronthaul network.
Implementation Method 1
The principle of this technique is to modulate a phase of an optical signal to a signal of a high frequency (frequency more than twice a bandwidth of the signal) and to emit interference noise out of a signal band
Data Source
AI summary
Proposed are an optimal operation method of a high-frequency dithering technique for compensating for interference noise in an analog optical transmission-based mobile fronthaul network, and a transmitter using same. An interference noise compensation method using high-frequency phase dithering performed in an analog optical transmission-based mobile fronthaul network may include the steps in which: a frequency-multiplexed wireless signal is converted in an optical transmitter to an intensity-modulated optical signal; and the phase of the optical signal intensity-modulated in the optical transmitter is dithered with an Orthogonal Frequency-Division Multiplexing (OFDM) signal.